Women are either bisexual or gay but "never straight", a new study has claimed. Women who class themselves as heterosexual are aroused by naked videos of both attractive men and women - whereas lesbians are far more attracted to the female form. Clips were played to women and their responses, including whether their pupils dilated when shown sexual stimuli, were recorded.

Experts from the University of Essex found straight women were strongly aroused by both sexes, even though they said they were only interested in men. In contrast, lesbians showed far stronger responses to women and barely any when shown the men. The researchers said lesbians were the most like men in their responses because it is usually men who show distinct sexual responses to their favourite sex.